The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
An aspect of the present invention relates to a laminated packaging material for a container comprising a substrate layer of paper and at least one other layer which contains at least a linear low density polyethylene.
Disposable packages for packaging products such as liquid foods are well known. A large group of these single use disposable packages is produced from a laminated packaging material comprising a core or substrate layer of paper or paperboard and outer coatings of thermoplastic material on both sides of the core layer. A commonly used thermoplastic material comprises low density polyethylene (LDPE).
The usual liquid-tight layers of LDPE material suffer from a number of drawbacks. A conventional LDPE-layer must be relatively thick in order to give a longitudinal sealing joint which is of sufficient mechanical strength and liquid tightness. In addition, a packaging laminate with outer layers of LDPE requires a relatively high thermosealing temperature, which consumes a relatively high amount of energy in the process.
Ethylene olefin copolymers produced by polymerisation in the presence of a catalyst with a single active site (“single site catalyst”), such as a metallocene catalyst, are known for their superior mechanical strength properties such as high toughness, elasticity and puncture resistance, even in a thin film. The ethylene copolymers produced in this manner, in case of a metallocene catalyst known as metallocene linear low density polyethylene (metallocene LLDPE or mLLDPE) or metallocene polyethylene (mPE), are known for good heat sealing properties at a considerably lower temperature than conventional LDPE. In addition, with metallocene LLPDE a narrow molecular weight distribution is obtained. However, metallocene LLDPE in pure form also suffers from a series of drawbacks, since in pure form poorer processing properties than LDPE in extrusion lamination are obtained.